Electrolytic condenser



Aug. 29, 1933. Y HAMMOND 1,924,606

ELECTROLYTIC counsnsmn Filed Nov. 8, 1928 2 Sheets-Sheet 1 [22 V67? forjazzrezayfi a/zwza/zd 2 Sheets-Sheet 2 L. HAMMOND ELECTROLYTIC CONDENSERFiled Nov. 8, 1928 Aug. 29, 1933.

g v k l l I l I I I IIA. IIIIIIIIL 5 j fiffforrzya w /Jav Patented Aug.29, 1933 ELECTROLYTIG CONDENSER Laurens Hammond, Evanston, 111.,assignonby mesne assignments, to Ralph D. Mershon, New York, N. Y.

Application November 8, 1928. Serial No. 318,085

12 Claims. (01. l75-363) My invention relates to an improvement in rent,for the operation of the filaments of therelectrolytic condensers and to.a filtering circuit mionic tubes in radio sets, or for other purposesin which s ch condensersmay be employed. The where substantially smoothdirect current is condensers I employ are of the general type ofdesired. the condenser invented by Edward F. Andrews I illustrate myinvention more or less diaand described and claimed in his co-pendingapgrammatically in the accompanying drawings,

piicaticn 1%)1347, filed on April 12, 1926. Each whereincondenserconsists essentially of a pair of metal- Figure 1 is a wiring diagram ofa circuit in he electrodes immersed in an electrolyte, the which mycells are employed; 10 condensersbeing adapted to function at low volt-Figure 2 is a wiring diagram of a testing circuit ages, the limit of thevoltage'at which they will below described; operate being fixed by thevoltage at which the Figure 3 is a wiring diagram of another testingwater of the electrolyte is continuously dissocircuit;

ciated into free hydrogen and oxygen gas. Figure 4 is a plan view of oneof my cells; 15 The electrolytic condensers of the type de- Figure 5 isa section along the line 5-5 of scribed may be employed as a condenserin filter Figure 4;

circuits carrying alternating or pulsating cur- Figure 6 is a verticalsection on an enlarged rents. In a filter circuit of the type shown inscale through one of the cell units; the above .co-pending applicationor in Figure 1 Figure '7 is a section on the line 7-'7 of Figure 20 ofthe present application, the impedance of 6; and such a cell orcondenser to alternating current Figure 8 is a diagrammatic illustrationof the is ex e .ingly small by comparison to its imrelation of theelectrodes of the cell shown in pedal e to the passage of a directcurrent. For Figure 6. I 7 use in such a circuit thebest functioningcell is Like parts are indicated by like symbols 25 one having a minimumimpedance to the passage throughout the specification and drawings.

of alternating current. For example, the alter- Referring first to thestructure of the connating current which will flow through thecirdenser, I employ any suitable outer housing or cuit including theinductance or choke coil will casing A which may for example be ofmetal. be inversely proportional to the relative imped- Positionedwithin it are a plurality of containers 3O ance of the circuit includingthe inductance and A which may for example be glass tubes having theimpedance of the condensers or cells G of one open end. Fig 1. In eachsuch tube are located positive and lectrolytic condensers or cells ofthe above negative electrodes herein shown as consisting type in generalfunction'best when they are opereach of three strips or ribbons of thedesired 65 at or near the gassing voltage. By that I material. Referringto Figure 6, B, B, indicate mean that the cells, during operation, areconthe srrips of the positive electrode preferably of ually liberatingsmall amounts of free oxygen nickel, and B B B indicate the strips ofthe aydrogen gas, which rises in the form of negative electrode, whichmay be of iron. Interbubbles and escapes from the cell. I have deposedbetween the strips are strips or ribbons veloped an improvement upon thecell of the B B of filter paper. In the formation of the general type ofthe above Andrews application, cell the strips or ribbons of metal andfilter which functions at voltages at which no free paper are rolled orcoiled together, as diagramgasses of any kind are liberated. Thecommercial matically shown, in Figure 8, to form a pack, and practicaladvantage of such cells lies in the the cross-section of which is shownin Figure '7.

p fact that the condenser may be sealed, after con- This pack ispositioned in the tube A into which struction, and will operatecontinuously thereis poured a suitable electrolyte, which may for afterlong as it is not subjected to a voltage example be an aqueous solutionof potassium rise sufficient to liberate free oxygen and hydrohydroxide.The ends of the electrode strips or gen from the electrolyte. Theefliciency of ribbons B B are secured together at the upper H such acondenser depends upon the particular end of the tube A and each groupof strips metals employed for its electrodes. constitutes a singleeffective electrode. By em- The circuit and cells herein described andploying such a composite electrode, with a plushown have manyapplications and uses. They rality of strips in parallel, I am able toobtain are particularly useful for delivering smooth dithe advantage ofthe exposal of a very large rect current, from a source of alternatingcursurface to the electrolyte, without the resistance as associated withthe filter circuit of Figure 1, I find it preferable to employ 12 cells,arranged in two series, one of 7 and the other of 5 cells.

I place'the 12 cells in the single container'A and make the connectionfrom cell to cell, as shown in Figure 5, the negative electrode orelectrode strips of one cell being soldered or otherwise secured to thepositive electrode strips of the adjacent cell, as at C, C. C indicatesthe terminal of the end cell of one series, and C the opposite terminalof the opposite end cell of the opposite series and C the commonintermediate terminal of the two series. In order to control the voltageof the individual cells I shunt each individual condenser cell, with ahigh resistance. In Figures 1 and 5 I illustrate the leads C extendingfrom the electrodes and the resistances C in circuit therewith.

In the actual assembly of the condenser, after the electrodev packs havebeen inserted in the individual cells and, the connections made, bysoldering or otherwise, and the electrolyte has been poured into eachcell the entire assembly is raised to a temperature approximating theboiling point, and a sealing compound D, for example of tar, is pouredinto the interior of the casing A in such fashion as to fill the entirespace above, between and beneath the containers A The tar, being lighterthan the electrolyte, will fill the upper portion of the individualtubes A The terminals C C and C are brought up through the top of thetar, but the individual cells and the remaining connections arepermanently and completely concealed within the housing. The result is.what is in effect a dry cell, so far as convenience of handling isconcerned and impossibility of losing or spilling the electrolyte.

Referring to the use of the condenser, as shown for example in Figure 1,E indicates a source of alternating current and E the primary coil of atransformer adapted to provide the desired voltage. a E diagrammaticallyindicates a rectifier adapted to allow the passage of current through itin but one direction, thereby causing a pulsating current to flow in thesecondary coil E of the transformer.

G and G diagrammatically indicate the two series of cells shown ingreater detail in Figures .4, 5, 6 and 7 above described, and Gindicates from the rectifier to the rheostat G. H leads from suchrheostat to the choke coil G and H extends from the choke coil to theload. H indicates'a conductive connection between the opposite end ofthe secondary coil E and the load G It will berealized that the wiringmay be interrupted or pieced out at various points, such as wherecontact is made with the'cell series G and G but the wiring diagram ofFigure 1, as above described, will indicate the circuit connections.

The operation of the filter circuit of Figure 1 is essentially the sameas that described and shown in the co-pending Andrews application101,347. The employment of an uneven number of cells across the inputand output on op- Referring to the wiring, I-I

posite sides of the choke coil does not of itself form part of thepresent invention and is described and claimed in the co-pending EdwardAndrews application No. 128,959, filed on August 13, 1926.

In the employment of scaled or non-gassing cells I find it necessary toprovide means for positively limiting the operating voltage tovoltagesiinsufiicient to cause gassing in the individual cells, sinceotherwise the generation of gas within the sealed cells might destroythe apparatus. I therefore employ supplemental res tanoe I which isconnected by the conductive line I with the line H and thus with therheostat G. From the opposite side of the resistance I extends the lineI with the terminal or contact I I is a pivoted conductive leaf, forexample of iron, normally resting upon any suitable support 1 hereinshown as screw threaded for vertical adjustment. I is a conductorextending from the leaf I to the line H. I is an electro-magnetconnected across the load by means of the conductors I I". W is a signallight in parallel with the resistance I and adapted to be actuated whenthe leaf or switch I is closed.

It will be understood that when an excess voltage is supplied and whenthe voltage across the load approaches the danger point, theelectro-magnet I is actuated and raises the leaf I nst gravity and intocircuit closing contact with the opposed switch element 1 The resistanceI is thus cut in across the load and to reduce the voltage, or toprevent its rise to the danger point. The signal light 1 is of use forexample when my condenser is applied to a radio set, the light in suchcase being preferably visible through the panel. When the user sees thatthe light is lighted he knows that the circuit through the resistance Ihas been closed and that therefore there is an excess voltage; Thisexcess voltage he can reduce by manipulation of the rheostat G to such apoint that the electro-magnet I is no longer actuated;

th circuit through the resistance I is then ken, and the light I goesout.

I have found that the efficiency of my condenser, depending on whatmetals are used for its electrodes, may fall off to a very marked extentwhen the cell is operated at a voltage of from to 1%,, volts per cell,as compared to its operation at a gassing voltage. The reason for thisbehavior is not entirely clear, but the principles involved may well beillustrated by reference to an experiment which shall now be described.

Referring to Figure 3 the secondary coil 0 is connected through analternating current ammeter d to two metallic electrodes a, b, whichmay, for example, be of pure nickel inserted in an electrolytic cell Xwhich may contain an aqueous solution of potassium hydroxide X The cellX also provided with a very small third electrode 6, which may forexample be a piece of nickel wire which is connected through the highresistance X and the double pole throw switch X with the storage batteryX Assume that'the switch is thrown so that the voltage of the battery isimpressed on the third electrode e, making it positive in relation tothe two electrodes a, b, which are of substantially the same averagepotential. In this case current will flow from 2 to a and b, liberatinga small amount of oxygen gas at the third electrode e and hydrogen gasat the electrodes, a, b, the

1,924,606 value ofthe current flow being 'limited to a few milliamperes'by the high, resistance X The transformer is now energized from anysuitable alternating source, and it will be found that only a very smallcurrent will flow in the circuit a, b, c, d, as indicated by the lowcurrent reading at the alternating current ammeter d. It willbe, let ussay, less than ampere. Thus, under the circumstances described, theelectrolytic cell has a high'impedance value to the passage ofalternating current.

It now the double pole double throw switch X is thrown to the oppositeposition, to cause a current to flow in the opposite direction in thecircuit which includes the third electrode 6 and the high resistance Xafter a short time hydrogen will be liberated at the third electrode eand a small amount of oxygen will be liberated by the electrodes a, 12.Even though the. current flowing in this manner is a very small amount,say a few milliamperes, the result will be that a large current, of twoto three amperes will flow through the circuit a, b, c, d, as observedon the ammeter d., These readings necessarily indicate that theimpedance to alternating current has decreased to a very great extent,and under these circumstances it may be said that the electrolytic cell,which previouslywas a poor condenser, has now become a good condenser.

From the above experiment it may be shown that nickel is a goodelectrode in such a condenser when it is surrounded by or saturated withor to some extent associated with oxygen gas, whereas it is a poorelectrode when associated with hydrogen gas.

The reason for this behavior is not altogether clear, and isparticularly difficult of explanation in the. case where iron electrodesare substituted for nickel. In this case the behavior of theelectrolytic cell is. exactlyuopposite to its behavior with nickelelectrodes, in that a large current will flow in the circuit a, b, c, d,when hydrogen gas is being liberated at the electrodes a and b, and onlyasmall current will flow when oxygen gas is being liberated at theseelectrodes. Thus the properties :of ironand nickel are in this respectopposite, nickel being a good electrode when associated with oxygen gasand iron being a good electrode when associated with hydrogen gas.

The third metal of'the iron group, cobalt, behaves unlike either iron ornickel, showing no strong tendency to behave differently, regardless ofwhether. oxygen or hydrogen is liberated by the electrodes.

From these experiments it would appear that every metal has certaindifinite characteristic properties which, so far as I am aware, have notheretofore been investigated. I am unable to find any allusion tothesecharacteristics in standard works on electro-cher'nistry or in theclassical theories dealing with this subject.

I have also investigated the characteristics of many other metals notincluded in the iron group and find them to behave in various ways whichI am frequently unable to predict except by trial. Very few metals arepermanent under such conditions of use, as they tend for the most partto go into solution. Metals of the iron group under some circumstancesappear to remain totally unaffected by the electrolytic action involved.

The impedance of an electrolytic cell to alternating current depends ontheimpedance to the passage of a current from one electrode to theelectrolyteand the impedance to the passage of a current from theelectrolyte to the surface of the other electrode. Unless a cell is usedin which the impedance to the passage of an alter nating current is lowat both electrodes, the impedance of the total cell will be high. Ittherefore follows that if a cell having both electrodes of nickel orboth of iron is used as a condenser, it will of necessity have a highimpedance when operated with a voltage drop across its electrodes ofbetween and 1 volts. is used as the positive electrode and iron as thenegative, the impedance will be low and the cell will function well as acondenser. If the polarity of the cell is reversed, nickel becoming thenegative and iron the positive, the impedance of the cell will rise tovalues which are many times greater.

These characteristics may be illustrated by another experiment showndiagrammatically in Figure 2, which is performed as follows.electrolytic cells 9, h, are connected in series together with analternating current ammeter i and the secondary coil 7' of thetransformer 9'.

By means of an auxiliary source of direct current, such as the storagebattery is acting through the potentiometer M, a direct current voltagemay be impressed across the electrodes of the electrolytic cells, takingthe electrodes 9 77, as positive relative to the electrodes 9 and 72 Ifthe electrodes g and h are of iron and the electrodes g and h are ofnickel, the combined impedance of the two cells in series will be low,the large current flowing through the ammeter giving a high reading. If,on the contrary, the electrodes g and h are of iron and the electrodes 9and h are of nickel, a very small reading will be obtained on theammeter. By varying the position of the potentiometer hi, the directcurrent voltage across the electrodes of the cells may be varied atwill.

If voltage of less than 1% volts, for example, is observed on the voltmeter k only a very small amount of current will flow in the circuit,the current being a fraction of a miliampere, and no free hydrogen oroxygen gas will be evolved from the electrolytic cells 9 and h. As thepotentiometer is adjusted and the voltage falls, the current indicatedby the ammeter will fall to a surprising extent.

voltage across them is reduced. In the case where nickel is the positiveand iron the negative, a very satisfactory amount of current can be madeto flow through them when the direct current voltage across them isbetween t; and 1%.; volts.

In combinations where nickel is used as the positive electrode and ironas the negative, or where a nickel positive and a cobalt negative areused, or where certain other metals are associated as negatives with anickel positive, no deterioration of the electrodes is apparent, evenupon continued operation for a long period of time.

I make use of these phenomena in the commercial application heretoforedescribed. I employ nickel as a positive electrode and I prefer toemploy iron as the negative electrode, although I do not wish to belimited to'the use of iron.

I wish it to be understood that where I employ in the claims the termsmeans for limiting the operating voltage to voltages at whichsubstantially no free oxygen and hydrogen is liberated I wish itunderstood that I refer to means outside of the condensers themselvessuch as over-volt- But if nickel Two The impedance of the cells 9 and Itfalls very rapidly as the direct current 1 hydrogen or oxygen or bothare evolved in use in such a wayas not to recombine but to be emittedfrom the cell. In the operation of these condensers it is possible forsmall amounts of oxygen, and hydrogen gas to be generated within thecells and to be alloyed with or absorbed by or in some way associatedwith the electrodes and which gasses during operation recombine to formwater. The theory of this is described in the co-pending Andrewsapplication 101,34'7, earlier referred to. Where I refer to free oxygenand hydrogen gas being liberated I mean that the gas is in such form aswould cause rising bubbles in the electrolyte or would build up apressure on the inside of a sealed container.

I have found that when a number of condenser cells are connected inseries and are operated below the gassing voltage that only an extremelyminute amount of direct current passes through the cells. If all thecells are not exactly alike, and in any commercial structure they neverare alike, I have found that there is a tendency for different cells tooperate at different average voltages, the sum of such voltages beingalways of course thevoltage across the group connected in series. Unlessspecial provision is made this effect may produce very undesirableresults affecting the efficiency of the apparatus to a large extent. Toobviate this difiiculty I'shunt each individual condenser cell with ahigh resistance which is equal or substantially equal for each cell.When a group of these cells is employed in a filter circuit such as thatshown in Figure 1 it is obvious that there will be a small loss ofdirect current through these resistances but this is an inappreciableamount if the value of the resistance is high enough.

On the other hand the voltage drop across each resistance will besubstantially equal and will serve to vmaintain the same averagepotential across each condenser cell of theseries. The resistances areindicated in Figures 1 and 5 as C".

Attempts have been made to make use of a variety, of differentelectrolytic cells adapted to function as condensers in filter circuitsand to operate them in such a way as to generate within the cells aslittle free gas as possible. If for instance a storage battery is usedin a filter circuit in place of my condensers it is possible to soregulate theinput and the output currents as to generate within thebattery during normal operation only a very slight amount of gas throughthe hydrolysis of water. In completing a commercial structure it will befound necessary to leave some egress for gasses, if they are generatedat all and at no matter how slow a rate, for it is obvious that if. anelectrolytic cell is hermetically sealed but continually generateswithin itself even the slightest trace of free gas the pressure willrise until the bursting point finallycomes. A storage battery of thelead acid type or an electrolytic cell consisting of lead plates insulphuric acid for instance whenused in such a circuit will sulphate toa certain extent. By this is meant that some of the lead of the plateswill combine with the sulphate radical in the sulphuric acid, thusliberating hydrogen. A cell of this type cannot therefore behermetically sealed in commercial practice.

Similarly an electrolytic. condenser of the forming type, such'as one,having an aluminum positive electrode in a borate, tartrate, or similarelectrolyte, requires the passage of a very small amount of directcurrent in order to maintain the dielectric film on the surface of thealuminum electrode.

While such condensers are madefor commercial purposes in vessels whichare substantially closed some egress is always provided to take care ofthe slight amount of the gas generated by electrolysis in the cell.

Wherever the smallest egress is allowed difficulties are experienced inshipment or sales resistance is shown by the public to the use ofdevices containing liquids which might be iniurious to fabrics orhousehold furnishing if spilled.

, 'I have found that by making use of the type ofcondenser disclosed inthe co-pending Andrews application No. 101,347, in which there issubstantially no oxide or hydroxide associated with the positiveelectrode of the condenser, it is entirely practical to manufacture ahermetically sealed electrolytic condenser which will give continuoussatisfaction if operated in connection 1 with a circuit which willpositively prevent a rise in voltage across the condenser which couldfree any gasses by electrolysis.

I claim: a

1. In combination, an electrolytic condenser 1 which includes electrodesand an electrolyte, a metallic positive electrode which does not combinechemically with the electrolyte, said electrode being free from anydielectric film, and means for limiting the operating voltage to volt- 1ages at which substantially no free oxygen or hydrogen is liberated.

2. In combination, an electrolytic condenser which includes electrodesand an electrolyte, a metallic positive electrode having substantially 1no oxide or hydroxide associated therewith, and means for limiting theoperating voltage to voltages at which substantially no free oxygen orhydrogen is liberated.

3. Incombination, an electrolytic condenser which includes electrodesand an electrolyte, a metallic positive electrode having substantiallyno oxide or hydroxide associated therewith, a gastight container forsaid condenser, and means for limiting the operating voltage to voltagesat 1 which substantially no free oxygen or hydrogen is liberated.

4. The combination with an electrolytic condenser, having a positive anda negative electrode, the positive electrode being of a metal of 1,

the iron group, and an electrolyte, of means for limiting the operatingvoltage to voltages at which substantially no free oxygen or hydrogen isliberated.

5. The combination with an electrolytic con- 1 denser, having a positiveand a negative electrode, the positive electrode being of nickel, and anelectrolyte, of means for limiting the operating voltage to voltages atwhich substantially no free oxygen or hydrogen is liberated.

6. The combination with an electrolytic condenser, having a positiveanda negative electrode, the positive electrode including nickel ineffective proportion, and an electrolyte, of means 1 for limiting theoperating voltage to voltages at which substantially no free oxygenorhydrogen is liberated.

'7. The combination with an electrolytic condenser, having a positiveand a negative electrode, the positive electrodebeing 0t andametal ofthe iron group, an electrolyte, and a substantially gas-tight containerfor said condenser, of means for limiting the operating voltage tovoltages at which substantially no free oxygen or hydrogen is liberated.

8. The combination with an electrolytic condenser, having a positive anda negative electrode, the positive electrode being of nickel, anelectrolyte, and a substantially gas-tight container for said condenser,of means for limiting the operating voltage to voltages at whichsubstantially no free oxygen or hydrogen is liberated.

9. The combination with an electrolytic condenser, having a positive anda negative electrode, the positive electrode including nickel ineffective proportion, an electrolyte, and a substantially gas-tightcontainer for said condenser, of means for limiting the operatingvoltage to voltages at which substantially no free oxygen or hydrogen isliberated.

10. The combination with a filter circuit containing one or moreinductances, and capacities which consist of one or more sealedelectrolytic cells, of means for limiting the operating voltage of saidcells to voltages at which no free oxygen or hydrogen is liberated.

11. The combination with a filter circuit containing one or moreinductances, and capacities which consist of one or more sealedelectrolytic cells, of means for limiting the operating voltage of saidcells to voltages at which no free oxygen or hydrogen is liberated,comprising a resistance and means for connecting it across said circuitat a predetermined excess voltage.

12. The combination with a filter circuit containing one or moreinductances, and capacities which consist of one or more electrolyticcells, of means for limiting the operating voltage of said cells tovoltages at which no free oxygen or hydrogen is liberated, andindicating means associated therewith adapted to be operated duringoperation of the voltage limiting means.

LAURENS HAMMOND.

ERTIF1GATE or EORRECTION.

Patent No. 1,924,606. August 29, 1933.

LAURENS HAMMOND.

It is hereby certified that error appears in the printed specificationof the above numbered patent reqeiring correction as follows: Page 4,line 150, claim 7, strike out the wore "and"; and that the said LettersPatent should be read with this correction therein that the same mayconform to the record of the case in the Patent Office.

Signed and sealed this 24th day of October, A. D. 1933.

F. M. Hopkins (Seal) Acting Commissioner of Patents.

(IERTIFIGATE 0F CORRECTION.

Patent No. 1,924,606. August 29, 1933.

LAU RENS HAMMOND.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page 4,line 150, claim 7, strike out the word "and"; and that the said LettersPatent should be read with this correction therein that the same mayconform to the record of the case in the Patent Office.

Signed and sealed this 24th day of October, A. D. 1933.

F. M. Hopkins (Seal) Acting Commissioner of Patents.

